This invention relates to a press for forming sheet metal and other materials, which includes an arrangement to compensate for deformation forces generated during the pressing operation.
In the process of forming of sheet metal, plastic or similar materials in a press, forces are generated which result in a bending of the sliding table and the press table. As a result, the formed workpieces are inexact and deformed, and the upper parts and lower parts of the tools are stressed excessively and non-uniformly because of the bending of the tool clamping plate.
One way to minimize bending with respect to the wearing of the tools, and the resulting inaccuracy of the finished parts, is to provide the bearing walls of the press table and the sliding table with a stiffer design. However, for reasons of weight and transport, this measure can be carried out only to a limited extent.
Sliding tables are known which can be moved out of the press for a change of tools, such as disclosed, for example, in German Patent Document DE 39 05 069 A1. Although a rigid design of bearing walls of the press table and of the sliding tables is not expressly addressed in this patent document, a measure of this type for the reduction of the bending during the forming appears implicit in the disclosure.
German Patent Document DE-OS 14 52 677 discloses an arrangement which automatically compensates for bending in the case of presses, by means of a pressure-compensating intermediate layer, which is enclosed on all sides. For this purpose, the intermediate layer is arranged on a side of the workpiece that faces the press components, between the tool and the press component which is subject to bending under the force of the pressure. A counterpressure device which acts upon the center of the crosshead is supported against an elastically deforming belt, and counterpressure is generated by means of straining screws or by the piston rod of a hydraulic cylinder.
It is an object of the present invention to compensate for bending during the forming of different workpieces and molds and the resultant varying pressure forces. It is a further object of the invention to provide an arrangement to counteract the physically unavoidable bending stresses in the tool clamping plate in order to maintain the tool clamping plate in a planar state.
A special advantage of the invention is the fact that the unavoidable deformation of the press table does not cause a defect in the tool clamping plate and in the tool. On the other hand, defects in the tool, which would otherwise require changing the tool, can be compensated by targeted variation in the bending of the tool clamping surface.
Another advantage of the invention is that, by means of the supporting devices, it can compensate not only for those bends which are caused by the deforming, but also those caused by sheet metal holding forces which may occur earlier, and therefore result in bending or deformation. Because the supporting devices are arranged in the corner areas of the sliding table, they support only a small portion of the load, the main load being borne in the area where the sliding table rests on the press table.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.